The purpose of this work is to greatly improve the performance of ultrasonic imaging transducers. Improvements are anticipated in range, and clarity of images, especially of chest cavity images, which require the greatest range of clarity. In addition, greater flexibility and lower noise levels will be achieved through signal conditioning at the transducer site. these improvements will be made by concerted work in four areas: 1. Evaluation of new transducer materials and composites. Literature of piezoelectic materials and devices will be constantly reviewed, and, when results appear to have use in medical imaging transducers, laboratory tests of the materials will be conducted. 2. Impedance and energy matching of transducers to aqueous media. Techniques to be investigated include geometric matching, multiple thin layer matching, and cooperative electical matching. 3. Novel transducer geometries and excitation methods. Novel transducer geometries include well matched linear and arc sector arrays, radial surface wave devices, and surface wave scanning arrays. 4. Thin film, thick film, and hybrid circuit technologies. Included in this category are the fabrication of microelectronic preamplifier circuits on the transducer and the formation of intricate conductor patterns on the transducer elements. Preliminary studies indicate that the tranducers which will be designed and built in our laboratories will have considerably greater efficiencies, wider bandwidths, lower noise, and higher output signal levels than any medical imaging transducers in existence today.